This application addresses broad Challenge Area (15) Translational science and specific Challenge Topic, 15-DK-102: Develop improved animal models of NIDDK diseases. Hepatitis C virus (HCV) is an agent of chronic liver disease, and affects an estimated 3% of the global population. Preventative and therapeutic options are severely limited;there is currently no vaccine available and non-specific, interferon-based treatments are frequently ineffective and have significant side effects. A small animal model for HCV replication would significantly expedite antiviral compound development and pre-clinical testing. Unfortunately, the species tropism of HCV is limited to humans and chimpanzees. Here we propose to address the need for a mouse model of HCV pathogenesis by systematically identifying and overcoming the blocks to infection in this species. Recently, we used an iterative cDNA screening approach to discover occludin (OCLN) as an essential HCV entry factor. We further determined that this molecule, along with human CD81, is the major determinant of HCV species restriction at the level of entry. Here we propose to apply these findings to the development of transient and stably transgenic mice, with the aim of modeling HCV entry in vivo. We then propose to address blocks to HCV RNA replication in murine cells using similar library screening approaches, as well as novel selectable genomes. The development of an inbred mouse model for HCV infection and replication will provide a much-needed platform for in vivo HCV vaccine and drug testing. We are requesting funds to hire a technician to assist in this work, along with significant expenditures for reagents and supplies required for these studies. This proposal thereby furthers the aims of the Recovery Act while potentially making important progress towards a small animal model for HCV PUBLIC HEALTH RELEVANCE: Hepatitis C virus (HCV) infects an estimated 4 million in the United States, and 130 million worldwide. Treatment options are limited and often ineffective. We propose to develop a mouse model of HCV infection by sequentially overcoming each block to its growth in murine cells. Development of a robust small animal model for HCV would greatly expedite pre-clinical testing of prevention and therapeutic strategies.